Comparison of two Algerian bentonites: Physico-chemical and retention capacity study

Abstract This paper presents the results of investigations on two Algerian bentonites (BentMag and BentMos), which may be considered for possible use in high level nuclear waste storage. The study concerns structural aspects and the chemical composition of the two bentonites (Bents). The effect of Na, Ca and K enrichment on cationic exchange capacity (CEC), specific surface area (SSA), dehydration and cation bonding selectivity has been examined. Results show that the BentMag contains more montmorillonite (Mt) and fewer impurities than BentMos. Ca and K treatments confer higher CEC and SSA to BentMag compared to BentMos. However, with Na treatment the two materials have similar CEC and SSA values. Nevertheless these values are higher compared to Ca and K treatments. Thermodynamic investigation shows that the dehydration energy is more important with Ca-treated bentonites than Na and K-treated one. Unlike BentMos, BentMag possesses the ability to retain water beyond 200 °C. The results of hydration kinetics studies show that water absorption is faster with Ca treatment, whereas the Na treatment allows a higher retention capacity of water. Also, higher vertical compaction of Na treated BentMag reduces its ability to retain water compared to Na treated BentMos which has less Mt.